Public water system · MT0000341
ActiveThompson Falls City of
At a glance
City of Thompson Falls (PWSID MT0000341) is an active community water system in Sanders County, Montana. It reports serving 1,950 people through 719 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2015.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
1,950
Service connections
719
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does City of Thompson Falls compare with other water systems in Sanders County?
By EPA's size categories, City of Thompson Falls is a small system (501 to 3,300 people). Sanders County has 44 active public water systems, and City of Thompson Falls is the largest of them by population served. Its population served is about 9.3 times the county average of 209 people per system, and accounts for 21% of the 9,212 people reported by systems filed under the county. Across Montana, the 2,378 active systems average 489 people each. Nationally, the average active community water system reports serving 6,703 people, so City of Thompson Falls is well below that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Montana has 853 active community water systems, 36% of the state's 2,378 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 1,994 Montana systems (84%) list groundwater as their primary source.
Who owns and regulates City of Thompson Falls?
EPA lists City of Thompson Falls as owned by a local government. The MT state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 7 of the 44 active systems in Sanders County (16%) are also owned by a local government.
Does City of Thompson Falls have drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2015. The violations listed here began between January 1994 and July 2015. By type: 10 monitoring and reporting, 1 public notice, recordkeeping or other and 1 required treatment not met. The contaminant or rule involved most often is Total coliform bacteria (TCR) (5 of them). EPA lists 12 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2015-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2005-11-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1999-12-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 1997-04-01 | Monitoring and reportingMonitoring, Repeat Major (TCR) · code 25 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1997-01-01 | Monitoring and reportingMonitoring, Repeat Major (TCR) · code 25 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1996-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 1994-10-01 | Monitoring and reportingMonitoring, Routine Minor (TCR) · code 24 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1994-06-01 | Monitoring and reportingMonitoring, Routine Minor (TCR) · code 24 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1994-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Bariumcode 1010 | No | Resolved |
| 1994-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Mercurycode 1035 | No | Resolved |
| 1994-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Seleniumcode 1045 | No | Resolved |
| 1994-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Chromiumcode 1020 | No | Resolved |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
City of Thompson Falls: frequently asked questions
Who runs City of Thompson Falls?
City of Thompson Falls (PWSID MT0000341) is a community water system owned by a local government. It is regulated by the MT state drinking water program.
How many people does City of Thompson Falls serve?
City of Thompson Falls reports serving 1,950 people through 719 service connections in Sanders County, Montana.
Where does City of Thompson Falls get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does City of Thompson Falls have any drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2015. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is City of Thompson Falls' water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2015. For current results, consult the system's annual water quality report, EPA ECHO, or the MT state drinking water program.
Where can I find City of Thompson Falls' water quality report?
As a community water system, City of Thompson Falls must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in Sanders County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Plains Town of | Sanders | 1,700 | Community | Groundwater |
| Hot Springs Municipal Water | Sanders | 600 | Community | Groundwater |
| One Stop | Sanders | 500 | Transient non-community | Groundwater |
| Sanders County Harvest Foods | Sanders | 445 | Non-transient non-community | Groundwater |
| Water Service Inc. Trout Creek | Sanders | 350 | Community | Groundwater |
| Noxon Water District | Sanders | 330 | Community | Groundwater |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Thompson Falls City of, PWSID MT0000341, Montana”, https://aquacensus.com/water-systems/montana/thompson-falls-city-of-mt0000341 (data as of October 1, 2026).